1. Field of the Invention
The present invention relates to marking devices for sheets of stock materials such as plates, tags and the like.
2. History of the Related Art
The customary type of such a device is provided with a vertical feed box in which are stacked the sheets. The inside walls of the box encircle the entire periphery of the sheets for their lateral support.
A conveyance unit moves the bottom sheet of the stack towards a marking head. After having been marked, the sheet in question is ejected from the marking area by the next sheet extracted from the lower portion of the stack.
All the marked sheets can be piled up on a receiver-chute or ejected in bulk.
Such a device presents, however, disadvantages in the sense that it is constituted by a great number of mechanical elements. Most of these elements are not adapted for sheet stock of different sizes so that it becomes necessary to change the majority of these elements with every change of size of the sheets to be marked.
Further, it is essential to control an exact guiding of the sheet stock along the conveyor elements in order to ensure a satisfactory positioning. Lastly, each sheet must be immobilized by clamping at the marking area in order to ensure a satisfactory quality of marking. This is achieved by relatively complicated clamping elements which increases the cost of the marking device.